SPOILER WARNING: This article contains major spoilers for "Enter Flashtime," the latest episode of The Flash.
"Crisis on Earth-X's" Mystery Girl has resurfaced on The Flash, but she brought no happy tidings this time around. In "Enter Flashtime," the latest episode, she bumped into Caitlin Snow and Earth-2's Harry Wells at C.C. Jitters. However, when they left, her smile became a frown, suggesting that she has some vendetta against one or the other.
At the end of the episode, Harry took Caitlin to C.C. Jitters. There, he asked her what was wrong. She explained that, for the very first time, she remembered what happened when Killer Frost took over. As she expressed her unease to Harry, Mystery Girl bumped into the table and spilled her coffee everywhere. She hurriedly grabbed some napkins to clean up the mess and anxiously over-explained her reason for being there: she was meeting someone.
Harry and Caitlin left in a hurry. On their way out, they wished her luck for her meeting. When they turned their backs, her smile faded and she looked much more serious. She then confirmed that her meeting had gone well -- which implies that she had intentionally bumped into them.
For the first time since she debuted, Mystery Girl has taken more serious approach to Team Flash. During “Crisis on Earth-X,” Barry Allen met the same young woman just moments before his marriage ceremony. Mystery Girl, a caterer at the event, was awestruck at meeting him. When she saw Ralph Dibney and Cisco Ramon at C.C. Jitters later on, she was similarly excited. So, her being serious about meeting Caitlin and Harry takes on some extra weight and may suggest that one of them -- probably Killer Frost -- is destined to do something unsavory in their future.
Though Mystery Girl has not yet received a name on the show, that hasn’t stopped fans from speculating about who she is. The prevailing theory is that she is playing Dawn Allen, Barry and Iris’ daughter. Dawn is also one of the Tornado Twins, a pair of superheroes from the future. Another theory speculates she is playing Jenni Ognats, Barry’s granddaughter and future superhero. In her last appearance in "The Elongated Knight Rises," she was seen writing in a notebook using the same glyphs Barry had written in right after he was pulled out of the Speed Force in the Season 4 premiere, which seems to confirm that she is indeed from the future.
Airing Tuesdays at 8 pm ET/PT on The CW, The Flash stars Grant Gustin as Barry Allen, Carlos Valdes as Cisco Ramon, Danielle Panabaker as Caitlin Snow, Candice Patton as Iris West, Jesse L. Martin as Joe West, and Tom Cavanagh as Harry Wells, with guest appearances from Hartley Sawyer as the Elongated Man.